Optimizing and improving patient morbidity and mortality outcomes is the primary objective of monitoring in critical and emergency care. Heart rate, respiratory rate, blood pressure (arterial and venous), blood oxygenation, and core temperature are the fundamental cardiovascular hemodynamic parameters that are continuously monitored for patients in critical and emergency care. From a systemic view, critical and emergency care monitoring can be summarized as a two-stage process. At the first stage, multiple sensors acquire vital biological signals corresponding to various physiological processes of the patient. At the second stage, a clinical information system is used to integrate and visualize the data from the multiple sensors used in first stage. State-of-the-art sensing technologies traditionally determine critical parameters from the vital biological signals, i.e., heart rate is determined either from electrocardiogram (ECG) or photoplethysmograph (PPG) using 12-lead electrodes or a fingertip pulse oximetry; respiratory rate is determined either from respiratory flow or respiratory/lung sounds using a plethysmograph or a pneumatograph; continuous blood pressure is determined by coupling the vascular pressures to a intravascular or extravascular pressure sensor through an arterial catheter; blood oxygenation from pulse oximetry, and core body temperature is measured using either a pulmonary arterial catheter or a urinary Foley catheter.
Traditionally, ECG is known for producing the highest quality measurement of heart rate, but it has been shown within the literature that heart rate measured from heart sounds is equally as reliable as ECG. Furthermore, the 12-lead ECG and respiratory data acquisition systems cause patient discomfort and restrict patient mobility. Though pulse oximetry is the gold standard monitoring technology for measuring blood oxygenation, the characteristics of the PPG signal are not fully understood among the medical community and it is still an area of active research. Also, blood oxygenation measurements of PPG are inaccurate when partial pressure levels of oxygen are high, and the inaccuracies also depend on properties of the skin which remain highly subjective. Accomplishing monitoring from the dynamics of the blood flow is currently limited to measurement of continuous blood pressure and core body temperature. Specifically, core body temperature sensing technologies require use of an additional catheter rather than using a preexisting arterial or venous line. Overall, the existing gold standard sensing technologies need multiple assessment systems in order to monitor critical cardiovascular hemodynamic parameters corresponding to various physiological processes. In addition, the existing clinical information systems face limitations to achieve medical device interoperability, as accomplishing the integration and synchronization of various data acquisition systems used in the first stage is complicated. Existing information systems also do not acquire and store high-resolution data. As a result, the complete morphology of the data acquired from various physiological sensors is not currently being used for clinical interventions. In addition, existing systems do not support the application of advanced data processing algorithms and as a consequence, providing real time support for clinical decision making still remains as an unsolved challenge.
From the above discussion, it can be appreciated that it would be desirable to have a system and method that can be used to determine critical physiological parameters without requiring multiple systems that each measures a discrete parameter.